The present invention relates to methods and devices for administering radiation and/or pharmaceutical or other therapeutic agents into bony tissues, especially vertebral bone. More particularly, the present invention relates to methods and devices for treating tumors in vertebral bone.
Methodologies utilizing localized radiation and/or pharmaceuticals and chemotherapeutic agents to treat many different types of tumors are well known in the art of medicine. One particular type of such treatment commonly referred to as brachytherapy, delivers a radiation dose to soft tissue tumors by way of a discrete radiation source that is positioned in or within close proximity to the tumor site. Most conventional brachytherapy typically utilizes radioactive granules, beads, or seed particles that are embedded or otherwise deposited at the tumor site through a series of cannulated needles or other brachytherapy apparatus. These techniques are useful in that, in contrast to external radiation therapies where the radiation dose is delivered through a beam that must often pass through healthy tissues, brachytherapy affords a more direct delivery of the radiation dose to the cancerous cells while minimizing undesirable radiation exposure to healthy cells.
Importantly, it will also be understood and appreciated by those skilled in the art that such brachytherapy systems may also be utilized to treat non-cancerous pathologies such as viral or bacterial infections and the like. Accordingly, these systems may be similarly adapted and utilized for the delivery of other therapeutic agents such as, but not limited to, chemotherapeutic compounds, gene therapy formulations, antibacterials, anti-fungals, etc.
Radiation therapy regimens are typically dependent upon the size and type of the tumor and it is often desirable to serially administer the therapy at different times within a day or over several days. In most conventional brachytherapy systems, which are primarily engineered for treating soft tissue tumors, the clinician typically guides either a brachytherapy needle assembly, catheter, or some other brachytherapy delivery apparatus into the tumor. The radiation source is subsequently delivered therethrough and the tumor is exposed to the desired dose of radiation. The delivery apparatus is then removed or electively left in place for subsequent treatment sessions. Optionally, the radiation source may be removed once the exposure time has elapsed.
One early brachytherapy technique, as disclosed in U.S. Pat. No. 4,402,308 to Scott, involves the use of sheathed needle injector for depositing radioactive “seeds” in a tumor. The injector comprises a hollow, needle sheath with a sharpened point suitable for injecting into human tissue and a slotted needle slidably and rotatably mounted inside the sheath. The sheath is retractable to expose the entire needle or any desired portion thereof.
The Scott patent, hereby incorporated herein by reference thereto, points out that it has been a common technique in the treatment of malignant tumors to inject radioactive seeds into a tumor to provide radiation therapy. These seeds are typically small discrete units filled with a radioactive material and sealed at each end. They may be of any convenient size although they are most often less than one millimeter in diameter and 3-4 millimeters in length. The number and positioning of the seeds in the tissue depends upon the treatment considered most appropriate by the physician.
Scott further points out that devices for accomplishing these implantation treatments have varied considerably. One of the first of such treatments is disclosed in U.S. Pat. No. 2,269,963 wherein a device having an appearance similar to that of a handgun, is utilized to deposit radioactive seeds by deploying a plunger into the barrel of the device. Techniques involving such guns or needles to implant seeds have proved to be deficient in many respects, primarily because they do not provide a means for implanting seeds at a precise spacing and location to perform the desired treatment. Accordingly, it is will be readily understood and appreciated by those skilled in the art that the more accurately a clinician can position and maintain a radiation source in a tumor, the more effective the sphere of radiation exposure will be.
Such deficiencies led Scott and others to seek alternative devices and methods by which radioactive seeds could be positioned in a fixed spaced relationship to each other, one method being the use of a suture containing the seeds in a predetermined array. After the suture was threaded into the tissue, the suture material would be absorbed by the body leaving the seeds positioned in a fixed spaced relationship. Such a suture approach had limited applicability in deep tissues so the same basic idea was employed using a needle to inject seeds separated by absorbable spacers.
Scott developed a sheathed needle injection device that was loaded with seeds but without any absorbable spacers. The sheathed needle device was intended for insertion into the tissue of interest whereupon the seeds were expelled from the needle through slots in the sheath. The entire sheathed needle device was subsequently withdrawn from the patient leaving the seeds deposited in the tissue. According to Scott, this device was a vast improvement over previous techniques yet it lacked some precision in positioning the seeds because the method of ejecting seeds from the needle functioned imperfectly. Subsequently, Scott developed a new and improved injector for implanting radioactive seeds in human tissue with precision as disclosed in the '308 patent.
Some shortcomings associated with the aforementioned devices and techniques are highlighted by U.S. Pat. No. 7,497,818 to Terwilliger, which is hereby incorporated herein by reference thereto. Terwilliger points out that despite any differences in the foregoing approaches, such techniques typically result in the radioactive seeds being deposited in the track made by the needle. As the needle is withdrawn, there is a tendency for the seeds to migrate in the needle track resulting in a poor distribution of the seeds and compromising the intended sphere of radiation. Terwilliger further points out that these seeds often continue to migrate over time resulting in the need for additional implant sessions that are costly and uncomfortable for the patient.
Terwilliger further notes that to address the foregoing problems, other prior art was developed to introduce seeds into the tumor site using a bioabsorbable, pre-manufactured, elongated assembly or implant that was capable of being loaded into an “introducer needle” prior to the procedure. Unfortunately, such implants have many drawbacks including positioning problems as well as the inability of the implant to flex with the tissue over the time necessary for the bio-absorbable material to dissolve. Moreover, as the tissue or gland recedes or shrinks back to pre-operative size, these implants often tend to remain stationary and do not move with the tissue. Accordingly, the final location relative to the tumor site is not maintained and the dosage of the radioactive seeds does not meet the preoperative therapy plan.
Terwilliger further cites U.S. Pat. No. 6,163,947 to Coniglione, also incorporated herein by reference thereto, wherein there is disclosed a string of hollow seeds as described in U.S. Pat. No. 5,713,828 that are strung onto a thin strand of suture material to form an array of seeds. This string of seeds is delivered into the tumor site placed within a hollow delivery needle. The difference in diameter between the seed and the thin suture material makes the assembly susceptible to collapse from axial force applied on the proximal end, thereby resulting in the assembly typically becoming jammed within the needle lumen and/or the assembly not maintaining the proper desired spacing between radioactive seeds as it is positioned into the treatment site.
To address the foregoing problems and to provide an alternative to the cited prior art, Terwilliger discloses a delivery system comprising a bioabsorbable, elongated implant having a plurality of radioactive seeds pre-dispersed therein in a prearranged orientation. The elongated implant member has sufficient axial rigidity in order to allow expulsion of the member while maintaining the spacing between seeds. The member is designed with enough flexibility/pliability to move in conjunction with the surrounding tissue as it shrinks back to a pre-operative size. According to Terwilliger, the seeds maintain their spacing, even after being introduced into the body, and this affords accurate placement and retention of the seeds in accordance with the physician's preoperative treatment plan.
Various implant alternatives to Terwilliger other than those cited above are also well known in the prior art. For example, U.S. Pat. No. 7,322,928 to Reed, which is also incorporated herein by reference thereto, discloses an absorbable suture member having radioactive seeds and spacer members predeterminantly disposed therein which is delivered through a conventional brachytherapy needle or the like. Other such implants include those disclosed in U.S. Pat. Nos. 7,329,259, 7,244,226, 6,264,600, 4,815,449, and 4,697,575, all of which are hereby incorporated herein by reference thereto.
As will be appreciated by those skilled in the art from a reading of the foregoing references, most of the conventional prior art brachytherapy devices and techniques utilize permanent or semi-permanent implantation of a radioactivity source at the tumor site often in a single treatment session. While the permanence of such implantation may be somewhat limited due to the radioactive half-life of the isotopes employed as well as the biodegradable nature of the containment housings or other vehicles implanted along with such isotopes, the permanence or semi-permanence is clearly a prior art shortcoming based upon the increased exposure of the patient to the resulting radioactivity over an extended period of time.
Additionally, the patient becomes an environmental source of radioactivity and must therefore avoid contact with certain people such as pregnant women and young children. Moreover, because the radioactivity remains in the patient for an extended period of time rather than affording a discrete and controlled exposure time, the use of higher radiation dosages and certain radioisotopes are often precluded for this type of technique. This, of course, limits the physician's flexibility in treatment regimens as well as the implementation of more aggressive radiation treatment strategies.
In addition to the brachytherapy implants referenced above, a variety of soft tissue brachytherapy techniques involving needle assemblies are also known in the prior art. Typically these techniques involve loading radioactive seeds into a series of needles that are then inserted into the treatment site, such as the prostate, utilizing ultrasound imaging to guide the insertion process. The radioactive seeds are positioned either independently within the needles or with spacers and expelled accordingly.
These needle assemblies can be fabricated in a variety of configurations such as, for example, those disclosed in U.S. Pat. Nos. 7,131,942 and 7,282,020, to Taylor and Kaplan, respectively, both of which are hereby incorporated herein by reference thereto. In particular, the '942 patent to Taylor discloses a brachytherapy needle assembly wherein a tubular sleeve containing discrete radioactive seeds is slidably and axially received within a needle that is, in turn, slidably positioned within an outer sleeve, the entire assembly being inserted into a soft tissue tumor to expel the radioactive seeds at the desired location. A stylet or obturator is driven through the tubular sleeve to deposit the seeds.
The '020 patent to Kaplan discloses a similar configuration wherein a stylet or obturator is slidably and axially received in a cannulated needle that, in turn, is slidably received in an outer sleeve. Radioactive seeds are positioned within the needle and the entire device is inserted into the patient. Once the device is in position, the stylet or obturator can be advanced to dispel the seeds in the desired location. In an alternative embodiment, the needle is replaced with a trocar that is similarly loaded with radioactive seeds. Other such needle assemblies include those disclosed in U.S. Pat. Nos. 7,361,135, 7,247,160, 7,104,945, 5,938,583, 5,928,130, 5,860,909, 4,815,449, and 4,697,575, all of which are hereby incorporated herein by reference thereto.
It will be understood and appreciated by those skilled in the art that all of the foregoing brachytherapy techniques and devices are primarily engineered for the treatment of soft tissue tumors. Spinal tumors as well as other tumors of the bone unfortunately create a unique challenge for these conventional brachytherapy techniques as the density of bone is significantly greater than that of soft tissues. Moreover, vertebral tumors have the added complication of proximity to highly sensitive neural and vascular anatomy further rendering conventional soft tissue brachytherapy apparatus and techniques unacceptable.
In particular, many of these soft tissue brachytherapy techniques require multiple needle insertions per treatment session to achieve an adequate sphere of radiation exposure at the tumor site. In the treatment of a vertebral tumor, this would result in increased risk to the patient's neural and vascular anatomy as well as additional complexities for the clinician who must forcibly insert multiple brachytherapy needle assemblies into vertebral bone. These shortcomings are even further complicated in the event that the patient's treatment regimen requires repeated, serial radiation exposures over several treatment sessions which may typically span over a few days or weeks. Such sessions are expensive and uncomfortable for the patient.
Additionally, similar to the radiation exposure problems observed in the implant technologies previously mentioned, these needle assemblies are typically designed to deliver discrete radiation particles that remain in the patient until the half-life of the radioisotope exhausts itself. Accordingly, the exposure considerations set forth above are not avoided by these brachytherapy alternatives. Moreover, unlike the implant technologies, these prior art needle assemblies do not address the problem of “seed migration” as discussed above.
U.S. Pat. Nos. 7,381,178 and 7,494,457 to Winkler, both of which are hereby incorporated herein by reference thereto, disclose various embodiments of a brachytherapy device for treating tumors in vertebral bone. The device includes a catheter member and a structural support member cooperatively attached thereto, the structural support member being designed to fit in an interstitial space that has been created by the surgical resection of the vertebral tumor. In particular, the device is designed to irradiate any cancerous remnants of the tumor that may appear in the margins of the excision. In one embodiment of the invention, a balloon catheter designed to be an inflated within the structural support member is used to deliver the radiation source.
One noteworthy shortcoming of the Winkler devices results from the dependency of the device's effectiveness on the previous excision of the tumor in conjunction with the placement of the support member within the interstitial space created by the excision. Such a treatment approach is clearly limited to situations conducive to such surgical intervention as well as anatomic constraints that may severely limit or prohibit the placement of the support member.
In light of the shortcomings of the foregoing prior art, it would be clearly advantageous for the clinician to have an alternative delivery method to apply radiation therapy or other therapeutic agents directly at bone tumor site within a vertebral body or other bony structure with a minimum amount of invasiveness and discomfort to the patient, especially where subsequent treatments sessions are desired.
Moreover, it would be similarly advantageous to deliver brachytherapy to a bone tumor without the problems of “seed migration” and extended exposure times that may compromise or prohibit the use of certain radioisotopes as well as high dosing regimens.